1. Field of the Invention
The present invention is directed to a device providing a protective enclosure within which tanks, such as those used for breathing apparatus, may be filled with a gas, such as air. In particular, the invention is directed to such a device which will not only provide maximum safety for all persons in the area of the device, in the event of an uncontrolled tank rupture during filling, but will also contain the forces generated by the blast of a high pressure cylinder to an extent sufficient to avoid potentially adverse effects which could result from a substantially free discharge of the rapidly expanding gases and sound burst which accompany a tank rupture.
2. Description of Related Art
Filling of tanks with gases of up to 350 bar (5,075 psig) can be extremely dangerous because of the hazard of explosion. The hazards comprise direct physical injury to persons in the surrounding area, such as from flying shrapnel produced by the exploding tank, and indirect hazards posed by the rapid discharge of expanding gas and the sound burst produced which can, for example, produce breakage of nearby windows. A device directed to the solution of this problem is disclosed in U.S. Pat. No. 3,817,299. However, the expansive gas protective device of this patent involves the use of a heavy wall cylindrical vessel having a door at its lower extremity through which a number of tanks, such as SCUBA diving tanks, may be placed into the vessel. The upper extremity of the vessel passes through the roof of the building within which the vessel is located to a terminus in the form of an open end of the vessel that is disposed above the roof and across which a gridwork of rods extends for preventing the escape of flying tanks and most debris to the surrounding environment. As a result, this vessel must be constructed in situ and requires modifications to the building structure within which it is to be housed. The lack of transportability of the completed, operational device and the need to implement building modifications to house it are both significant disadvantages.
U.S. Pat. No. 4,505,309 discloses an apparatus for inflating pneumatic tires on vehicular wheel rims that comprises a box that receives a tire-carrying wheel rim. The box has walls (for surrounding the tire-carrying wheel rim, on all sides and at the top and bottom) that are formed, for example, of at least one-quarter inch thick steel plates that are welded together to be sufficiently strong to contain all tire and wheel parts in the event that the tire explodes. Furthermore, one wall of the box serves a door that is openable to permit the introduction and removal of the tire-carrying wheel rim and, for example, a 1/16th inch gap extends all around the door so that a total leakage area of at least about 20 square inches will exist for the harmless escape of air from the box when a tire in the box explodes. For tire inflation purposes, a flexible air conduit is provided within the box that has an outlet connector that can be clamped to a tire valve stem and which has linking means that penetrates through a wall of the box to a valve supply line outside the box and to a pressure indicator which will indicate the pressure in the tire from outside of the box. While the device of this patent may be more than adequate to prevent damage from occurring as a result of a tire exploding during inflation, such an apparatus would not eliminate hazards associated with charging of compressed gas tanks from several standpoints.
Firstly, since compressed gas tanks are charged up to pressures of at least 100 to 500 times that used for inflating a tire, the strength of the walls, of which the enclosure of U.S. Pat. No. 4,505,309 is formed, would be inadequate to safely resist the force of an exploding tank of highly pressurized gases. Furthermore, even if the walls did not rupture, the device as a whole lacks sufficient mass to prevent the apparatus from "jumping" under the forces of the explosion in a manner producing injury to a person or damage to anything upon which the apparatus lands. Still further, an air gap of the magnitude disclosed in this patent is such that, in the event of an explosive rupturing of a pressurized gas tank within the enclosure, the rate at which the expanding gases will be discharged from the enclosure would increase the ambient pressure of the room sufficiently to damage its windows, doors and/or roof, and the same would apply to the discharge of a potentially hazardous sound burst from the explosion.
Another type of explosion relief device is known for use with large vessels of the type requiring full vessel diameter venting, wherein the force of an explosion occurring within the vessel causes a removable head or hatch cover to move away from the vessel to allow the compressed gases produced by the explosion to escape through the, now open, top without damaging other parts of the vessel. Such vessels are used for a wide variety of functions, e.g., a reactor, separator, storage tank, bin, container, hopper, surge tank, etc., and an example of a vessel having an explosive relief cover can be found in U.S. Pat. No. 3,788,514. However, since full vessel diameter venting is used to minimize the necessary pressure rating of a vessel, i.e., to reduce the thickness of the vessel wall to the greatest extent while still enabling it to meet desired safety standards, if applied to an enclosure that is small enough to be transportable, the enclosure would lack sufficient mass to preclude the above-noted jumping phenomenon and the rapid discharge of pressure out of the full diameter of the vessel, during venting, would lead to the above-noted problem of, for example, windows being blown out due to an increase in ambient room pressure.
Accordingly, there is a need for a protective enclosure device for filling of tanks with compressed gas which is sufficiently compact to be transportable in a fully assembled operable state, requires no modifications to building structure in order to enable its use, and which will sufficiently contain the effects of an uncontrolled tank rupture within the device so as to avoid any damage to persons and objects in its vicinity.